In an X-ray computed tomography (CT), it is demanded to improve quantitativity of a CT value. As an imaging method for improving quantitativity of the CT value, for example, there have been proposed a dual energy CT (DECT) and a photon counting CT (PCCT). The DECT is for simply discriminating a material using projection data of two types of X-ray energy. The PCCT is an improved imaging method having higher quantitativity compared to the DECT. As well known in the art, in the PCCT, it is necessary to count X-ray photons one by one. In order to prevent an overflow in the X-ray photon measurement (count loss or pile-up of X-ray photons), an upper limit of a dose rate (dose on unit area per unit time) is inevitably set to be low. Meanwhile, the dose according to the X-ray transmitting through an examinee and arriving at an X-ray detector has a dynamic range of 16 bits or wider. For this reason, data of a high dose with a high overflow risk and data of a significantly low dose with a lot of noises are mixed in data used in an image reconstruction of the PCCT. When the PCCT data acquisition is executed under a condition for avoiding an overflow, data of the significantly low dose becomes dominant, and a noise caused by a measurement error increases.
It is an object of embodiments to provide an X-ray imaging apparatus, a wedge filter apparatus, and a method of controlling a wedge filter capable of reducing an overflow risk and a dynamic range.